1. Technical Field
The present invention relates to the use of vortex valves and nozzles in coal slurry fuel handling, control and injection to improve the useful life of control hardware and to permit atomization of the coal slurry fuel at lower pressures than have been heretofore possible. The invention has particular utility in internal combustion fuel injection systems to control the injection of diesel oil and coal slurry type fuel into an engine cylinder during the combustion process.
2. Discussion of the Prior Art
Internal combustion engines exhibit poor efficiency when fuel is not atomized properly by the injector nozzles, especially when certain types of fuel, such as coal/water, coal/diesel fuel, and low grade diesel fuels, are employed. The problems associated with atomization are compounded in slurries which are highly viscous, non-Newtonian fluids in which viscosity varies with shear rate, temperature and, in many cases, the past history of the fuel storage and delivery systems. To overcome this problem the trend has been toward higher injection pressures. High injection pressures (i.e., above 6,000 psi) require proportionately smaller injector nozzle port areas to pass an equivalent amount of fuel into the engine. Typical fuel injector systems used in diesel engines with diesel fuel require one or more very small injection ports (e.g., 0.25 to 0.50 mm) and injection pressures on the order of 5,000 to 10,000 psi to atomize and disburse the fuel in the engine combustion chamber. When coal slurry fuels are employed, the pressures required for optimum atomization are generally much higher (i.e., 15,000 to 30,000 psi), which means that the injection ports must be proportionately much smaller. The smaller nozzles tend to become clogged with solid coal particles and ash content in coal slurry fuels. This, plus the tendency of such fuels to shear thin and then re-thicken at increasing shear rates, combined with the high injection pressures and the correspondingly higher flow velocities through small nozzles, tends to clog the nozzles and produce increased wear due to erosion. In addition, the char particles that are produced during combustion tend to create deposits which clog the small injection nozzles. Further, the principal limiting factor in the use of high injection pressures is the relatively high cost and high reliability requirements placed upon the precision components that must supply fuel at pressures in the 6,000 to 20,000 psi range. These combined problems place a practical limit on the maximum pressures which can be pumped reliably, resulting in achieving less than optimum atomization in present coal slurry engines.